The survival of Lactobacillus hilgardii, a highly ethanol-tolerant organism, after an ethanol challenge at 25% (v/v) for 10 min, increased by several log cycles when cells, grown in the absence of ethanol, were pre-treated with 10% (v/v) ethanol, 15% (v/v) methanol or 2% (v/v) butanol for 4 h. A temperature upshift (25 to 40 degrees C) before ethanol challenge demonstrated a similar enhancement of apparent resistance to ethanol. Ethanol shock enhanced apparent resistance to methanol, butanol and heat challenges. The addition of chloramphenicol to cells prior to any pre-treatment did not significantly diminish the increase in ethanol tolerance, suggesting that de novo protein synthesis is not required for induced tolerance in this organism.